[nRF24] Implemented getPacketLength

src/modules/nRF24.cpp

@@ -1,6 +1,6 @@
 #include "nRF24.h"
 
-nRF24::nRF24(Module* mod) : PhysicalLayer(NRF24_CRYSTAL_FREQ, NRF24_DIV_EXPONENT) {
+nRF24::nRF24(Module* mod) : PhysicalLayer(NRF24_CRYSTAL_FREQ, NRF24_DIV_EXPONENT, NRF24_MAX_PACKET_LENGTH) {
   _mod = mod;
 }
 
@@ -161,7 +161,7 @@ int16_t nRF24::startTransmit(uint8_t* data, size_t len, uint8_t addr) {
   (void)addr;
 
   // check packet length
-  if(len > 32) {
+  if(len > NRF24_MAX_PACKET_LENGTH) {
     return(ERR_PACKET_TOO_LONG);
   }
 
@@ -239,19 +239,13 @@ int16_t nRF24::readData(uint8_t* data, size_t len) {
      return(state);
   }
 
-  // read payload length
-  uint8_t buff[1];
-  SPItransfer(NRF24_CMD_READ_RX_PAYLOAD_WIDTH, false, NULL, buff, 1);
-
-  size_t length = buff[0];
+  // get packet length
+  size_t length = len;
+  if(len == NRF24_MAX_PACKET_LENGTH) {
+    length = getPacketLength();
+  }
 
   // read packet data
-  if(len == 0) {
-    // argument 'len' equal to zero indicates String call, which means dynamically allocated data array
-    // dispose of the original and create a new one
-    delete[] data;
-    data = new uint8_t[length + 1];
-  }
   SPIreadRxPayload(data, length);
 
   // add terminating null
@@ -479,6 +473,13 @@ int16_t nRF24::setFrequencyDeviation(float freqDev) {
   return(ERR_NONE);
 }
 
+size_t nRF24::getPacketLength(bool update) {
+  (void)update;
+  uint8_t length = 0;
+  SPItransfer(NRF24_CMD_READ_RX_PAYLOAD_WIDTH, false, NULL, &length, 1);
+  return((size_t)length);
+}
+
 void nRF24::clearIRQ() {
   // clear status bits
   _mod->SPIsetRegValue(NRF24_REG_STATUS, NRF24_RX_DR | NRF24_TX_DS | NRF24_MAX_RT, 6, 4);

src/modules/nRF24.h

@@ -9,6 +9,7 @@
 // nRF24 physical layer properties (dummy only)
 #define NRF24_CRYSTAL_FREQ                            1.0
 #define NRF24_DIV_EXPONENT                            0
+#define NRF24_MAX_PACKET_LENGTH                       32
 
 // nRF24 SPI commands
 #define NRF24_CMD_READ                                0b00000000
@@ -398,6 +399,15 @@ class nRF24: public PhysicalLayer {
     */
     int16_t setFrequencyDeviation(float freqDev);
 
+     /*!
+      \brief Query modem for the packet length of received payload.
+
+      \param update Update received packet length. Will return cached value when set to false.
+
+      \returns Length of last received packet in bytes.
+    */
+    size_t getPacketLength(bool update = true);
+
   private:
     Module* _mod;